The human body includes arterial and venous conduits which run throughout various sections of the human body. These conduits conduct blood into and from the heart which maintain the circulation that helps to sustain the metabolic events in the body. The vessels undergo biological, physiological, and mechanical changes depending on the body metabolism which determine the functionality of the wall of the artery.
Sometimes the wall of an artery becomes occluded due to deposits of fatty tissues which in turn form plaque on the walls of the artery. These plaques then have to be removed to restore the normal function of the artery. One known mechanism of removing the plaque is to compress the plaque against the wall of the artery using a balloon catheter. This procedure is called Percutaneous (under the skin) Transluminal (under x-ray guidance) Coronary (region of intervention) Angioplasty (plaque compression) or PTCA.
For a PTCA procedure to be accomplished, a balloon catheter and a guidewire along with a guiding catheter are typically required. The guiding catheter is normally introduced in a groin artery and pushed upwards towards the aorta until it reaches the mouth of the coronary artery. Once the guiding catheter is placed at the opening of the coronary artery, a highly floppy wire is introduced into the guiding catheter such that the wire crosses the mouth of the guiding catheter and goes into the coronary artery. It then has to reach the site of the lesion (plaque) which is usually a very tortuous route and the operator (the cardiologist) has to struggle to reach the guidewire in place. Once a guidewire has crossed the lesion, it is then pushed distally to the lesion so that it remains at a safe place. This is to ensure that the wire does not slip out of the lesion.
In addition to angioplasty, balloon catheters are used for balloon septostomy, wherein the balloon enlarges an opening in the heart for greater blood flow, and tuboplasty, wherein the balloon is used to correct a fallopian tube obstruction. Balloon catheters are further used to deliver stents, or round wire forms which are typically used to provide support to a blood vessel, and for installing filters, to prevent migration of blood clots in the treatment of thrombophlebitis.
Frequently, it may be advantageous to deliver a substance which helps to address the core problem, aid in healing, or prevent recurrence of the problem. This is addressed, for example, in U.S. Pat. No. 5,810,767 to Klein, wherein a balloon is provided with pockets which, when the balloon is inflated, are filled with a liquid therapeutic substance. The objective in Klein is to maintain the balloon in contact with the body lumen, whereby the liquid is maintained within the pockets against the body lumen as it is infused, and is not quickly swept away with blood flow. In this manner, treatment to the body lumen may be maintained while the balloon is inflated.
In Klein, however, the application of a therapeutic substance only takes place while the balloon is inflated. To maintain blood flow, the balloon must be repeatedly deflated for a period of time, then reinflated to resume treatment. Thus, the period of treatment is thus necessarily short, and terminates once the surgical procedure is over, and the catheter is removed.
Another approach to delivering a therapeutic substance may be found in U.S. Pat. No. 7,055,237 to Thomas. Thomas does not disclose the advantages of delivering a substance using a balloon catheter itself as the delivery device. Rather, the reference discloses a stent as the delivery device, the stent itself being delivered by catheter. In Thomas, the stent is fabricated with a series of indentations or dimples in the surface of the stent, which act to increase the amount of drug the stent can be coated with. In use, the stent is expanded against the vessel wall, whereupon the drug is released.
In Thomas, drug is delivered only while the stent remains in the body. Where it is intended for the stent to remain in the body for an extended period, the delivery time period may be adequate. Where it is not necessary to leave an implant in the body, however, Thomas fails to provide a solution.
In U.S. Pat. No. 6,364,856 to Ding et al., however, a balloon catheter as well as a stent is used to deliver a biologically active material or drug to a lumen wall. In Ding, a non-hydrogel sponge having a plurality of voids is formed around the balloon. A non-hydrophilic substance to be delivered is incorporated into the sponge. As the balloon is inflated, the non-hydrophilic substance is squeezed out of the sponge, where it diffuses into contacting tissue. Again, however, delivery is effectively halted when the balloon is removed. In addition, as in the previous references, once the balloon has been withdrawn, the radiopaque marker within or near the balloon which identifies the location of the treatment site is also removed.
In U.S. Pat. No. 5,102,402 to Dror et al., a balloon catheter has a coating containing microcapsules, whereby the coating may be released from the balloon onto the lumen, and where the microcapsules are crushed during inflation, releasing their contents. A radiopaque compound may be incorporated into the microcapsules, whereby the vessel may be visualized by fluoroscopy or similar methods.
In Dror, however, even if a coating is transferred to the lumen wall, all of the crushed microcapsules release their contents at once, where much of the therapeutic or radiopaque substance may be washed away by the flow of materials within the lumen.
There remains, therefore, a need to prolong the application of the therapeutic substance at the treatment site, while maintaining radiopaque marking.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 CFR §1.56(a) exists.